种植密度对不同株高夏玉米品种茎秆性状与抗倒伏能力的影响

倒伏是影响夏玉米在密植条件下获得高产的重要限制因素之一，本研究旨在探讨种植密度对不同株高夏玉米品种茎秆性状与抗倒伏能力的影响。以矮秆品种登海661 (DH661)和高秆品种鲁单981 (LD981)为试验材料，通过设置4.50×10⁴株 hm^-2、6.75×10⁴株 hm^-2和9.00×10⁴株 hm^-2 3个种植密度，研究茎秆节间长度、茎秆穿刺强度、茎秆显微结构以及倒伏率等方面的变化。结果表明，随种植密度增加，夏玉米的基部第3茎节间和穗位节间变细，茎秆穿刺强度显著下降，较密度4.50万株 hm^-2，DH661和LD981 6.75万株 hm^-2、9.00万株 hm^-2地上第3节间茎秆穿刺强度分别降低了8.5%、22.6%和13.3%、29.6%；茎秆皮层和维管束内部厚壁细胞厚度及维管束数目均随种植密度的增加显著下降，倒伏风险增加，但矮秆品种的下降幅度小于高秆品种，而产量的增加幅度大于高秆品种，说明矮秆品种在高密度下能够保持较好的抗倒伏性能，有助于其在高密度种植条件下获得高产、稳产。

Effects of Plant Density on Stem Traits and Lodging Resistance of Summer Maize Hybrids with Different Plant Heights

Lodging is an important factor limiting grain yield of summer maize at high plant density. Two summer maize hybrids with different plant heights, namely the short-plant height hybrid Denghai661 (DH661) and the high-plant height hybrid Ludan981 (LD981), were used to study the relationship between stem traits and lodging resistance of summer maize hybrids at 45 000 plants ha^-1, 67 500 plants ha^-1 and 90 000 plants ha^-1. With the increase of plant density, stem diameter and rind penetrometer resistance of summer maize were significantly decreased. Rind penetrometer of 3rd basal node of DH661 at 67 500 plants ha^-1 and 90 000 plants ha^-1 decreased by 8.5% and 22.6%, while those of LD981 decreased by 13.3% and 29.6%, respectively, compared with that at 45 000 plants ha^-1. In addition, with the increase of planting density, the cortex thickness, vascular bundle sheath thickness, and vascular bundle number were significantly decreased, resulting in the increase of lodging rate. However, the extent of variation in these parameters was less for short-plant height hybrid than for high-plant height hybrid, and the yield of short-plant height hybrid was greater than that of high-plant height hybrid, indicating that short-plant height hybrid has better resistance to lodging with high yield at high plant density.